What is the term for any molten rock within the earth?

• A. Geothermal Gradient
• B. Magma
• C. Igneous Rock
• D. Mantle Keels

Answer: (B)

Magma. It is molten rock that exists beneath the Earth's surface, formed when rocks melt due to heat and pressure in the crust or upper mantle. Magma can contain crystals and dissolved gases, and because it is less dense than surrounding solid rock, it tends to rise and pool in magma chambers. When magma cools underground, it solidifies into intrusive igneous rocks like granite or diorite; when it erupts onto the surface, it is called lava and forms extrusive rocks as it cools rapidly. The other terms don’t describe molten rock inside the Earth: a geothermal gradient is the temperature increase with depth; igneous rock refers to the solidified product of magma; mantle keels is not the standard term for molten rock.